High-dose preoperative radiotherapy does not alter the strength of unilaterally irradiated colon anastomoses in rats

Purpose: We studied the influence of preoperative radiotherapy on the stren gth of colon anastomoses in rats. We compared a conventional (2 Gy/fraction ; 1 fraction/day; 5 days/week; cumulative doses of 40.0, 60.0, and 80.0 Gy) and a hyperfractionated schedule (1.6 Gy/fraction, 2 fractions/day, 5 days /week, cumulative doses of 41.6, 60.8, and 80.0 Gy). We compared unilateral ly with bilaterally irradiated anastomoses for two conventional radiation s chedules. Methods and Materials: The rectosigmoid was always irradiated. Depending on the experiment, the cecum was irradiated or not. A side-to-side anastomosi s between rectosigmoid and cecum was constructed the day following the last irradiation. The strength of the anastomosis was evaluated by means of a b ursting pressure (BP) measurement after 10 days. A control group and a sham -treated group were carried out. Results: Compared to controls, the strength of unilaterally irradiated anas tomoses was not altered and BP values were independent of the radiation sch edule and of the cumulative dose. In case of bilaterally irradiated colon a nastomoses, anastomotic strength was significantly reduced at 80 Gy, but no t at 40 Gy. Conclusions: After high doses of preoperative radiotherapy, colon anastomos es in rats can be safely constructed if only one anastomotic segment is irr adiated. The strength of bilaterally irradiated colon anastomoses is dose-d ependent. (C) 1999 Elsevier Science Inc.